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Alkaline Phosphatase (ALP) Blood Test: What Your Results Mean

Alkaline phosphatase (ALP) is an enzyme found mainly in the liver, bile ducts, and bones. It plays a role in breaking down proteins and is released into the bloodstream when these tissues are damaged or very active. ALP is a key marker in evaluating liver and bone disorders. Levels naturally vary with age, sex, and growth stages — children and adolescents often have higher ALP due to active bone growth.

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Normal Range

44 – 147 U/L

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Unit

U/L

What Your Results Mean

Normal

A normal ALP level indicates no significant damage or unusual activity in the liver, bile ducts, or bones. The liver is producing and excreting ALP at a healthy rate, and bone turnover is within normal limits.

High

High ALP most commonly indicates liver or bile duct disease — especially cholestasis (blocked bile flow), hepatitis, or cirrhosis. It is also elevated in bone disorders such as Paget's disease, bone fractures, bone metastases, and hyperparathyroidism. In children, high ALP can be normal due to bone growth.

Low

Low ALP is less common and may indicate hypothyroidism, zinc deficiency, pernicious anaemia, or rare inherited conditions such as hypophosphatasia — a genetic disorder affecting bone mineralisation.

Frequently Asked Questions

What does high ALP mean? expand_more
High ALP usually indicates a liver or bile duct problem — particularly cholestasis (blocked bile flow) — or a bone disorder such as Paget's disease or bone metastases. GGT is often checked alongside ALP: if GGT is also elevated, the source is likely the liver or bile ducts.
Is high ALP always serious? expand_more
Not always. High ALP is normal in children and teenagers due to bone growth, and it rises during pregnancy (from the placenta). In adults without these explanations, elevated ALP should be investigated with additional liver and bone tests.
What is the normal ALP range? expand_more
For adults, the normal range is roughly 44 to 147 U/L, though this varies by laboratory and differs by age and sex. Children can have much higher values during growth spurts.
How is high ALP treated? expand_more
Treatment depends on the underlying cause. Liver or bile duct conditions may require medications, endoscopic procedures, or surgery. Bone-related causes are managed according to the specific diagnosis — for example, bisphosphonates for Paget's disease.
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